Study of the applied current asymmetry of the spin-torque interaction

This thesis describes experimental work that is designed to address unresolved issues in domain-wall dynamics that have emerged from recent scientific work on magnetic field and electric-current driven domain-wall dynamics in permalloy microstructures. A principle issue involves nonlinear effects in the electric-current driven domain-wall velocity under reversal of electric current. Existing theoretical models of the spin-torque effect (responsible for electric-current driven domain-wall motion) do not allow nonlinear current response. Other issues are related to magnetic-field and electric-current driven Barkhausen jumps in magnetic microstructure. Sample preparation and characterization studies reported provide the technical basis for improved experiments that should resolve the stated unsettled scientific issues.Physic

Process Safety Enhancement in Chemical Plant Design by Exploiting Accident Knowledge

The accident rate in the chemical industry has not been decreasing although they could be prevented by using the existing knowledge. The aim of this thesis is to enhance the utilization of knowledge from earlier accidents especially in the designing of chemical plants. The experience feedback on accidents is improved by analyzing and disseminating knowledge on accident contributors to design activities. The research was done by analyzing the 364 chemical process accident reports available in the Failure Knowledge Database (FKD). It was found that the technical contributors (79%) dominated the accidents in the CPI. Deeper analyses were carried out to identify the accident contributors, and design and operation errors for the six most common equipment types of accidents. The other indicators of accidents included in the study were; the contributors share as main contributor (SMC), equipment specific contributors, and the combination of high SMC and frequency. In design and operation errors analyses, the study found that about 80% of the accident cases were contributed by at least one design error with an average of 2.3 errors per accident. The timing of the errors was analyzed and it shows that about half (47%) of the design and operation errors were made during the process design-oriented stages. Thus, more focus should be given in the making of fundamental decisions such as process conditions, chemicals and reactions during the early phases of the design. The corrective actions proposed in accident reports employed typically the outer layers of protection such as procedural changes (53% of cases) even though the design errors are generally dominant. The inherently safer design proposed was only 18% of cases; and these were based on the most used principles which were ’error tolerance’ and ‘moderate’. Current design oriented safety methods do not fully utilize knowledge from earlier accidents and therefore do not facilitate learning. For example, HAZOP is often employed only as a final check and do not support the designer during the work. Therefore the thesis proposed a method for identification of accident contributors and design errors throughout the design stages by utilizing knowledge from earlier accidents. The method is based on information obtained from accident contributors and design errors discovered which will be presented in the first part of this thesis. The aim is to show also their mechanisms and time of creation. The proposed method would support the design process by having an early design error detection and elimination through design changes. Therefore, cost and safety benefits can be achieved by undergoing changes in the earlier stages of plant design. The Bhopal tragedy is used as the case study to demonstrate and test the method. The proposed method could be used to predict an average of up to 85% of accident contributors

Health risk assessment due to emissions from medical waste incinerator in Malaysia

In this research, health risk assessment due to the emission of pollutants from a medical waste incinerator located within industrial estate in the northern part of Malaysia was presented. The influence of pollutants emission in the vicinity of the incineration plant was the main concern in this research. The measured emissions of pollutants from the stacks of the studied plant that may pose risk to human health and the environment are compared against the acceptable limit as in the Environmental Quality (Clean Air) Regulation 2014. Next, the levels of pollutants in ambient air are assessed in comparison with the guideline established by the Malaysia Ambient Air Quality Guideline (MAAQG). The health risk assessment was then conducted by calculating the quantitative risk for non-carcinogenic and carcinogenic pollutants. The study reveals that the total cancer risk due to emission of carcinogenic pollutants from the incinerator is 1.84 × 10-5, which indicates risky circumstances as the calculated risk is higher than the benchmark of acceptable risk of 1 × 10-6. Meanwhile the health risk calculated due to emission of non-carcinogenic pollutants ranges between 0.000286 and 0.1, indicating acceptable risk. The result shows that the non-carcinogenic pollutants emitted from the studied medical waste incinerator are within the acceptable exposure limits. However, for carcinogens, the released amounts may cause human health risk, and therefore demands for further attention to reduce the concentrations as low as reasonably practicable, at least in compliance with the established guidelines

Process hazard analysis of gasification process by using oil palm empty fruit bunch as feedstock

Production of hydrogen rich gas from the gasification of biomass to replace fossil fuels has become a common interest worldwide. One of the potential biomass in Malaysia to produce hydrogen rich gas is empty fruit bunch (EFB) from oil palm (Elaeis guineensis). Numerous researchers have carried out studies on hydrogen production using biomass but there are limited researches on the hazards analysis incorporated in the gasification process of EFB. This paper presents the hazards identification and risk reduction of the gasification process by using EFB as a feedstock. The research aims to incorporate safety needs to the gasification process of EFB for safe operation in the future. The process hazards analysis has been carried out on process unit namely fire burner, feeding hopper, fluidised bed reactor and cyclone. The potential hazard, possible causes, risk and consequences of the process unit were analysed. Based on the analysis, the major hazards identified in the process are overpressure and over temperature followed by the release of hydrogen gases. Safe by design is the most effective risk reduction strategy since it can eliminate the hazards from the source by having inherently safer design of the hydrogen process plant

The effect of conventional and microwave heating techniques on transesterification of waste cooking oil to biodiesel

This research is focused on the effect of processing parameters such as molar ratio of sample to solvent (1:3 - 1:15), catalyst loading (0.5 - 2.5 wt %), temperature (40 - 80 C) and time of reaction ( 5 - 180 min) on the transesterification yield of waste cooking oil (WCO) in conventional thermal heating and microwave heating technique s . The analysis carried out revealed that the microwave assisted transesterification produced a comparable yield to conventional heating transesterification with ~ 5 times faster in heating up the reaction mixture to a reaction temperature and reduced ~ 90% of the reaction time required . This study concludes that microwave assisted transesterification , which is a green technology, may have great potential in reducing the processing time compared to conventional thermal heating transesterification

Emergency management: implementing a whole community approach

Emergency indicates unfortunate reminders of the susceptibility of communities. Emergency affects communities and individuals, disrupts the functions of social, technical structures and the economy, and suggests ways to change emergency management procedures. Efficient emergency management, however, focuses on implementing the emergency planning at all levels of the government and non-government sector, including individuals and community organisations. Therefore, the whole community approach to emergency management includes the government, communities and individuals at all levels, while responding to emergencies. The contents of this study propose a strategic framework for most leading emergency management communities, even whole community concepts into their everyday activities. The goals of this analysis are to evaluate the entire group response to emergency management for improved emergency management outcomes. Meanwhile, the objective of this study is to assess the whole community approach in managing emergencies and the community achieving better results in emergency management. The mixed-method approach is adopted for the data collection. This literature review has identified three principles of the whole community approach: Recognising and addressing the actual needs of the whole community, integrating and supporting all members of the community, and improving what works best in daily communities. In addition, these principles complement the approaches that provide a starting point for those who are learning about the whole community and an effective framework for emergency management

Hydrogen gas production from gasification of oil palm empty fruit bunch (EFB) in a fluidized bed reactor

Malaysia is one of the largest producers of palm oil and this industry plays an important role in Malaysia economic growth. As this industry grows larger, a significant amount of oil palm waste is generated, creating the problem of overloading biomass waste. Since the oil palm waste has many significant uses such as empty fruit bunches (EFB), the interest in production of hydrogen gas as the renewable energy from EFB also increases. The most common and favorable thermochemical processes to produce the hydrogen gas is gasification process in fluidized bed reactor. Regardless of tremendous experimental studies done on effectiveness of using EFB for production of hydrogen, the process implementation in industry is still discouraging. This is due to lack of proven technology and high capital cost of investment. In this study, a computational modeling was developed for EFB gasification in fluidized bed gasifier using the ASPEN PLUS simulator (v. 8.8) to optimize the gasification temperature, pressure and to study the different of chemical behavior. The results indicated that increase in temperature will increases the production of hydrogen and enhances carbon conversion efficiency. The optimum temperature and pressure was 850 °C and 1.035 bar respectively. The result shows that the char was removed significantly after several gas cleaning process. The final product for purified hydrogen gas is 14.5 kg/hr which is around 21% of hydrogen yield. Based on the result, it indicates that EFB has a potential to be used as a source of energy in a future

Process development of oil palm empty fruit bunch gasification by using fluidised bed reactor for hydrogen gas production

Hydrogen can store and deliver usable energy, but it does not typically exist by itself in nature and must be produced from compounds that contain it such as biomass. Hydrogen can be used as fuel which produce from gasification process that used renewable sources as feedstock. Large amount of empty fruit bunch (EFB) has been produced in Malaysia and yet has no specific used in large quantity and it is being incinerated or used as landfill material dumped in the plantation. These situations have led to increased CO2 and other greenhouse gas (GHG) emissions in the atmosphere. During preliminary study, it shows that there are very limited studies being done in the process design development of the hydrogen production by using EFB from oil palm. Despite of tremendous experimental studies done on the effectiveness of using EFB for production of hydrogen, the process implementation in industry is still discouraging. This is due to lack of proven technology and high capital cost of investment. In this study, the drying, gasification and purification unit operations were modelled in Aspen Plus simulator for production of pure hydrogen gas and char was removed significantly after several gas cleaning processes. The final product for purified hydrogen gas is 12.3 t/h which is 16.3 % of hydrogen gas produced from the total EFB feedstock. Based on the result, the optimum temperature and pressure for gasification process is 850 °C and 1 atm respectively. Since, there is not much research have been carried out on process design of hydrogen production process by using EFB as feedstock, the understanding towards this topic can be prolonged